Chapter 6
Vision
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• Chapter 6 Outline
• The Stimulus
• Anatomy of the Visual System
• Coding of Visual Information in the Retina
• Analysis of Visual Information:
Role of the Striate Cortex
• Analysis of Visual Information:
Role of the Visual Association Cortex
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• Vision
• Sensory _______________
• A specialized __________ that detects a particular
category of _________________ events.
• Sensory __________________
• The process by which sensory stimuli are transduced
into slow, graded ____________ potentials.
• Receptor potential
• A slow, graded electrical potential produced by a
receptor cell in response to a physical __________.
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• The Stimulus
• Perceived color of light is determined by:
• Hue
• Determined by _______________
• Brightness
• Determined by the ______________ of the
electromagnetic radiation
• Saturation
• Determined by the ___________of the light wave
• White light is a blend of all wavelengths, if white light
is added to a monochromatic light it becomes
unsaturated - pastel
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Electromagnetic spectrum
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• Anatomy of the Visual System
• The eyes
• _____________
• Bony pockets in the front of the skull.
• Sclera
• The ____________ tissue of the eye.
• Conjunctiva
• Mucous membranes that line the eyelid and protect
the eye. Prevents objects from
___________________________________________
_______________________________________.
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• Anatomy of the Visual System
• The eyes
• Cornea
• ______________________________ of the eye that
admits light.
• Pupil
• Adjustable opening in the ___________ that
regulates the amount of light that enters the eye.
• Iris
• __________________________ situated behind the
cornea.
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• Anatomy of the Visual System
• The eyes
• Lens
• Consists of a series of transparent, onion-like
layers. Its shape can be changed by
________________________________________
________________________________.
• ______________________
• Changes in the ________________of the lens,
accomplished by the ciliary muscles, that focus
images of near or distant objects on the retina.
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• Anatomy of the Visual System
• The eyes
• ____________
• The neural tissue and photoreceptive cells located
on the inner surface of the posterior portion of the
eye.
• Photo______________
• One of the receptor cells of the retina; transduces
photic energy into electrical potentials
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• Anatomy of the Visual System
• The eyes
• __________ (120 million)
• Photoreceptor cells of the retina, sensitive to the
• light of low intensity.
• _______________ (6 million)
• Photoreceptor cells of the retina; maximally
sensitive to one of three different wavelengths of
light and hence encodes color vision.
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• Anatomy of the Visual System
• The eyes
• ____________
• Region of the retina that mediates the most acute
vision of birds and higher mammals. Color
sensitive cones constitute the only type of
photoreceptor found in the fovea.
• _______________
• The location of the exit point from the retina of the
fibers of the ganglion cells that form the optic
nerve; responsible for the ______________.
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• Anatomy of the Visual System
• The eyes
• Bipolar cell
• A bipolar neuron located in the middle layer of the
retina, conveying information from the
____________________________.
• Ganglion cell
• A neuron that receives visual information from
bipolar cells; its
_______________________________________
_______________________________________.
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• Anatomy of the Visual System
• The eyes
• _________________cell
• A neuron in the retina that interconnects adjacent
photoreceptors and the outer processes of the bipolar
cells.
• _____________________cell
• A neuron in the retina that interconnects adjacent
ganglion cells and the inner processes of the bipolar
cells.
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• Anatomy of the Visual System
• Photoreceptors
• Lamella
• A layer of membrane containing ______________;
found in rods and cones.
• Photopigment
• A protein dye bonded to retinal, a substance derived
from vitamin ___; responsible for the transduction of
visual information.
• Opsin
• A class of protein that, together with retinal,
constitutes the photopigments.
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• Anatomy of the Visual System
• Photoreceptors
• Retinal
• A chemical synthesized from vitamin A, joins with
an opsin to form a _________________.
• ________________
• A particular opsin found in __________.
• In the dark adapted state it appears _________.
• In the bleached state the color changed to
_________.
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• The action of light on some neurons in the visual
system.
• Photoreceptors are ___________________by light.
• Hyperpolarization causes a reduction in the
•
•
•
photoreceptor’s release of the neurotransmitter
______________.
Because glutamate normally hyperpolarizes the
bipolar cell, the reduction in glutamate causes the
bipolar cell to ______________.
The relative depolarization of the bipolar cell causes
the ganglion cell to ___________________.
Thus light ____________ the ganglion cell.
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• Anatomy of the Visual System
• Connections between eye and brain
• Dorsal -___________________________
• A group of cell bodies within the lateral geniculate
body of the thalamus; receives inputs from the
retina and projects to the primary visual cortex.
• Magnocellular layer
• One of the two inner layers in the dorsal lateral
geniculate nucleus; transmits information
necessary for the perception of form,
________________, depth, and small differences
in brightness to the primary visual cortex.
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• Anatomy of the Visual System
• Connections between eye and brain
• Parvocellular layer
• One of the four outer layers of neurons in the
dorsal lateral geniculate nucleus; transmits
information necessary for perception
________________________________________
________________________________________
• Koniocellular sublayer
• One of the sublayers of neurons in the dorsal
lateral geniculate nucleus found ventral to each of
the magnocellular and parvocellular layers;
transmits information from short-wavelength
cones to the primary visual cortex.
• These two layers are responsible
________________________________________
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________________________________________
• Anatomy of the Visual System
• Connections between eye and brain
• Calcarine fissure
• Horizontal fissure on the inner surface of the
posterior cerebral cortex; the location of the
primary visual cortex.
• Striate cortex
• The primary visual cortex.
• Optic chiasm
• A connection between the optic nerves, located
below the base of the brain, just anterior to the
pituitary gland.
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• Coding of Visual Information in the Retina
• Coding of Light and Dark
• Receptive Field
• That portion of the visual field in which the presentation of
visual stimuli will produce an alteration in the firing rate of
a particular neuron. If the neuron receives information
from receptors located in the fovea, the receptive field will
be at the point the eye is looking. If the input is from
receptors in the peripheral retina, the receptive field will
be off to the side, or above or below where the eye is
looking.
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• Coding of Visual Information in the Retina
• Photoreceptors: trichromatic coding
• _________________
• An inherited form of defective color vision in which
red and green hues are confused;
__________________________________________
_________________________________________.
• They see the world in shades of yellow and blue;
both red and green look _____________to them.
• Visual acuity is normal.
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• Theories of color vision coding.
• Trichromatic – any color can be reproduced by mixing
three colors selected along the spectrum.
• Opponent-process – ________________of color
• Red-green
• Blue-yellow
• Black-white
• Produces complimentary colors
• Color vision yields the ability to distinguish
________________________________________.
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• Coding of Visual Information in the Retina
• Photoreceptors: trichromatic coding
• ________________
• An inherited form of defective color vision in which red
and green hues are confused;
______________________________________________
____________________________________________.
• Visual acuity is normal.
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• Coding of Visual Information in the Retina
• Photoreceptors: trichromatic coding
• _______________
• An inherited form of defective color vision in which
hues with short wavelengths are confused;
________________________________________
______________________________________.
• See the world in greens and reds.
• Blue looks green and yellow looks pink.
• Visual acuity is normal.
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• Analysis of Visual Information: The Striate Cortex
• Anatomy of the striate cortex
• David Hubel and Torsten Wiesel
• 1960s at Harvard University
• Discovered that neurons in the visual cortex did not
simply respond to light; they selectively responded to
____________________ of the visual world. The
receptive field size exceeds that of a single ganglion cell.
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• Analysis of Visual Information: The Striate Cortex
• Orientation and movement
• ______________ cell
• An orientation-sensitive neuron in the striate
cortex whose receptive field is organized in an
opponent fashion.
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• Analysis of Visual Information: The Striate Cortex
• Orientation and movement
• ______________ cell
• A neuron in the visual cortex that responds to the
presence of a line segment with a particular
orientation located within its receptive field,
especially when the line ____________
perpendicular to its orientation.
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• Analysis of Visual Information: The Striate Cortex
• Orientation and movement
• ____________________ cell
• A neuron in the visual cortex that responds to the
presence of a line segment with a particular
orientation that ___________ at a particular point
within a cell’s receptive field.
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• Analysis of Visual Information: The Striate Cortex
• Spatial frequency
• _______________ grating
• A series of straight parallel bands varying
continuously in the brightness according to a sinewave function, along a line perpendicular to their
lengths.
• Cortical cells tend to respond ___________ to sine
wave gratings than bars
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• Analysis of Visual Information: The Striate Cortex
• Spatial Frequency
• Spatial frequency
• The relative width of the bands in a sine-wave
grating, measured in
__________________________________________
__________________________________________.
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• Analysis of Visual Information: The Striate Cortex
• Retinal Disparity
• Retinal disparity
• The fact that points on objects located at different
distances from the observer will fall on slightly
different locations on the two retinas; provides the
basis for _____________ or depth perception
• Some neurons respond __________to images that
are produced by retinal disparity.
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• Hypercolumns and retinotopic maps
• The _______ is very small (about 2 degrees of visual
•
•
angle, and is about 1/1000 of the area of the retina.
In the striate cortex about 25% of the cortex is devoted
to the analysis of the fovea.
______________________________for foveal
processing in the cortex.
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• Analysis of Visual Information: The Striate Cortex
• Color
• Cytochrome oxidase (CO) __________
• The central region of a module of the primary visual
cortex, revealed by a stain for cytochrome oxidase;
contains ______________________; part of the
parvocellular system.
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• Analysis of Visual Information: The Visual
Association Cortex
• _________________ cortex
• A region of the visual association cortex; receives
fibers from the striate cortex and from the superior
colliculi and projects to the inferior _________ cortex.
• Regions respond to particular _____________of
visual information such as orientation, movement,
spatial frequency, retinal disparity, or color.
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• Analysis of Visual Information: The Visual
Association Cortex
• _______________ stream
• A system of interconnected regions of the visual
cortex involved in the perception of spatial location,
beginning with the striate cortex and ending with the
posterior ______________ cortex.
• _______________ stream
• A system of interconnected regions of visual cortex
involved in the perception of form, beginning with the
striate cortex and ending with the inferior
____________ cortex.
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• Analysis of Visual Information: The Visual
Association Cortex
• Color constancy
• The relative constant ____________ of the colors of
objects viewed under varying __________conditions.
• This ability compensates for the perception of the
___________________ under different lighting
conditions.
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• Analysis of Visual Information: The Visual
Association Cortex
• Studies with humans
• Cerebral _________________
• Inability to discriminate among different hues; caused
by damage to the visual association cortex.
• Damage to V4 disrupts ________________, but not
the ability to discriminate between colors.
• Damage to TEO (V8) disrupts __________________
(and __________ for colors), but not the ability to
distinguish between shades of gray.
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• Analysis of Visual Information: The Visual
Association Cortex
• Studies with humans
• _____________
• Inability to perceive or identify a stimulus by means of
a particular sensory modality.
• Visual agnosia
• Deficits in visual perception in the absence of
_______________; caused by brain damage.
• Apperceptive visual agnosia
• Failure to ____________________ even though
visual acuity is relatively normal.
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• Analysis of Visual Information: The Visual
Association Cortex
• Analysis of form
• _________________
• Failure to recognize particular people by the sight of
their ____________.
• Associative visual agnosia
• Inability to ___________________ that are perceived
visually, even though the form of the perceived object
can be drawn or matched with similar objects.
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• Analysis of Visual Information: The Visual Association
Cortex
• _________________ area
• A region of the extrastriate cortex located at the base
of the brain; involved in perception of faces and other
objects that require expertise to recognize.
Individuals with ______________ show a deficit in the
ability to recognize faces, and the fusiform facial area is
weakly activated when individuals look at faces.
• Akinetopsia
• Inability to perceive___________, caused by damage to
area V5 of the visual association cortex.
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Subjects with
visual object
agnosia may be
able to
recognize a
face, but not the
vegetables that
compose it.
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• Analysis of Visual Information: The Visual Association
Cortex
• Perception of movement
• Extrastriate body area (EBA)
• A region of the visual association cortex located in the
lateral occipitotemporal cortex; involved in perception of
____________________________________________.
• Parahippocampal place area (PPA)
• A region of the medial temporal cortex; involved in
perception of particular places (_______________).
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• Analysis of Visual Information: The Visual Association
Cortex
• Perception of movement
• ________________
• The complex motion of points in the visual field caused by
relative movement between the observer and
environment; provides information about the relative
_______________of objects from the observer and of the
relative ____________________.
• Akinetopsia
• Inability to perceive movement, caused by damage to
area V5 of the visual association cortex. Unable to
______________________________________________
_____________________________________.
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V5: damage produces akinetopsia
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• Analysis of Visual Information: The Visual Association
Cortex
• Perception of spatial location
• Intraparietal sulcus
• The end of the dorsal stream of the visual association
coretex; involved in perception of __________, visual
_______________, and control of eye and head
movements..
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• Dorsal and Ventral Pathways
• What is it?
_____________ pathway.
• Where is it and how do I engage it?
_______pathway.
• Involved in control of
_________________________________________
_________________________________________
_________________________________________
_________________________________________
________________________________________.
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